Preheat oven to 200C Fan.
Gently heat olive oil in a non-stick frying pan and sauté the onion, garlic, and red pepper for about 3 minutes until softened. Turn off heat.
Stir in frozen peas and red chilli flakes to warm peas through.
Break the eggs into a medium mixing bowl, whisk eggs, add the yogurt, and beat together well, then season with salt and pepper.
Spray a medium-sized ovenproof quiche / flan dish with low-calorie cooking spray or wipe with a little olive oil.
Add sauteed vegetables to quiche dish and mix in sliced mushrooms.
Pour egg mixture over, season and sprinkle over the grated cheese.
Place in the centre of oven and bake for 25-30 minutes until the eggs have set and the frittata is browned, and cheese is bubbling.
Remove from the oven and allow to rest for 5 minutes. Cut into wedges and serve with a simple salad of lettuce, cucumber, spring onions and tomato.